docs/NDK-GDB.html - platform/ndk - Git at Google

 <html><body><pre>'ndk-gdb' Overview

 IMPORTANT: IF YOU ARE DEBUGGING THREADED PROGRAMS, PLEASE READ THE
            SECTION BELOW TITLED 'Thread Support'.

 I. Usage:
 ---------

 The Android NDK r4 introduced a helper shell script named 'ndk-gdb' to
 easily launch a native debugging session for your NDK-generated machine code.

 The script is located at the top-level directory of the NDK, and shall
 be invoked from the command-line when in your application project
 directory, or any of its sub-directories. For example:

     cd $PROJECT
     $NDK/ndk-gdb

 Where $NDK points to your NDK installation path. You can also create an
 alias or add $NDK to your PATH to avoid typing it every time.

 IMPORTANT: Native debugging can only work if *all* these conditions are met:

     1. Your application is built with the 'ndk-build' script:

         Building with the legacy "make APP=&lt;name&gt;" method is not
         supported by ndk-gdb.

     2. Your application is debuggable:

         In other words, your AndroidManifest.xml has an &lt;application&gt;
         element that sets the android:debuggable attribute to "true"

     3. You are running your application on Android 2.2 (or higher):

         ndk-gdb will not work if you try to run your application on
         previous versions of the system. That does not mean that your
         application should target the Android 2.2. API level, just
         that the debugging session should happen on a 2.2+ device or
         emulator system image.

         IMPORTANT IMPORTANT IMPORTANT !!

             If you are using the ADT Eclipse plug-in to build your
             application, make sure you're using version 0.9.7 or
             later.

             If you are using the 'ant' build tool, make sure that you
             have the latest revision of the SDK Platform components.
             The following minimal revisions are required:

                 Android 1.5      r4
                 Android 1.6      r3
                 Android 2.1      r2
                 Android 2.2      r1

             These should be available through the SDK updater.

             If these conditions are not met, the generated .apk will
             not contain required support files and native debugging
             will not be possible.

 'ndk-gdb' handles many error conditions and will dump an informative error
 message if it finds a problem. For example, it:

     - checks that adb is in your path.

     - checks that your application is declared debuggable in its manifest.

     - checks that, on the device, the installed application with the same
       package name is also debuggable.


 By default, ndk-gdb will search for an already-running application process,
 and will dump an error if it doesn't find one. You can however use the --start
 or --launch=&lt;name&gt; option to automatically start your activity before the
 debugging session.

 When it successfully attaches to your application process, ndk-gdb will give
 you a normal GDB prompt, after setting up the session to properly look for
 your source files and symbol/debug versions of your generated native
 libraries.

 You can set breakpoints with 'b &lt;location&gt;' and resume execution with 'c'
 (for 'continue'). See the GDB manual for a list of commands.

 IMPORTANT: When quitting the GDB prompt, your debugged application process
            will be stopped! This is a gdb limitation.

 IMPORTANT: The GDB prompt will be preceded by a long list of error messages,
            where gdb complains that it cannot find various system libraries
            (e.g. libc.so, libstdc++.so, liblog.so, libcutils.so, etc...)

            This is normal, because there are no symbol/debug versions of
            these libraries corresponding to your target device on your
            development machine. You can safely ignore these messages.

 II. Options:
 ------------

 To see a list of options, type 'ndk-gdb --help'. Notable ones are:

   --verbose:
     Print verbose information about the native debugging session setup.
     Only needed to debug problems when you can't connect and that the
     error messages printed by ndk-gdb are not enough.

   --force:
     By default, ndk-gdb aborts if it finds that another native debugging
     session is running on the same device. Using --force will kill the
     session, and replace it with a new one. Note that the debugged program
     is *not* killed and will be stopped again.

   --start:
     By default, ndk-gdb will try to attach to an existing running instance
     of your application on the target device. You can use --start to
     explicitly launch your application before the debugging session.

     NOTE: This launches the first launchable activity listed from your
           application manifest. Use --launch=&lt;name&gt; to start another one.
           See --launch-list to dump the list of such activities.

   --launch=&lt;name&gt;:
     This is similar to --start, except that it allows you to start a specific
     activity from your application. This is only useful if your manifest
     defines several launchable activities.

   --launch-list:
     Convenience option that prints the list of all launchable activity names
     found in your application manifest. The first one will be used by --start

   --project=&lt;path&gt;:
     Specify application project directory. Useful if you want to launch
     the script without cd-ing to the directory before that.

   --port=&lt;port&gt;:
     By default, ndk-gdb will use local TCP port 5039 to communicate with
     the debugged application. By using a different port, it is possible
     to natively debug programs running on different devices/emulators
     connected to the same development machine.

   --adb=&lt;file&gt;:
     Specify the adb tool executable, in case it is not in your path.

   -d, -e, -s &lt;serial&gt;:
     These flags are similar to the ADB ones and allow you to handle the
     case where you have several devices/emulators connected to your
     development machine.

         -d:          Connect to a single physical device
         -e:          Connect to a single emulator device
         -s &lt;serial&gt;: Connect to a specific device or emulator
                      where &lt;serial&gt; is the device's name as listed
                      by the "adb devices" command.

     Alternatively, you can define the ADB_SERIAL environment variable
     to list a specific device, without the need for a specific option.

   --exec=&lt;file&gt;:
   -x &lt;file&gt;:
     After connecting to the debugged process, run the GDB initialization
     commands found in &lt;file&gt;. This is useful if you want to do something
     repeatedly, e.g. setting up a list of breakpoints then resuming
     execution automatically.


 III. Requirements:
 ------------------

 At the moment 'ndk-gdb' requires a Unix shell to run. This means that
 Cygwin is required to run it on Windows. We hope to get rid of this
 limitation in a future NDK release.

 The other NDK requirements apply: e.g. GNU Make 3.81 or higher.


 IV. Thread Support:
 -------------------

 If your application runs on a platform older than Android 2.3, ndk-gdb will
 not be able to debug native threads properly. Instead, the debugger will only
 be able to put breakpoints on the main thread, completely ignoring the
 execution of other ones.

 The root of the problem is complex, but is essentially due to a very unfortunate
 bug in the platform, which was only discovered lately.

 The gdbserver binary that comes with this NDK has special code to detect this
 condition at runtime and adapt its behaviour automatically (in other words,
 you don't have anything special to do when building your code).

 What this means in practical terms are:

 - If you are on Android 2.3, or a prior platform release which has had the
   platform bug-fix back-ported to it, you will be able to debug native
   threads automatically.

 - If you are not, you will only be able to debug the main thread
   (as in previous NDK releases). You will also see the following message
   when launching ndk-gdb (just before the gdb prompt):

      Thread debugging is unsupported on this Android platform!

   If you place a breakpoint on a function executed on a non-main thread, the
   program will exit with the following message in GDB:

         Program terminated with signal SIGTRAP, Trace/breakpoint trap.
         The program no longer exists.

 </pre></body></html>
	<html><body><pre>'ndk-gdb' Overview

	IMPORTANT: IF YOU ARE DEBUGGING THREADED PROGRAMS, PLEASE READ THE
	SECTION BELOW TITLED 'Thread Support'.

	I. Usage:
	---------

	The Android NDK r4 introduced a helper shell script named 'ndk-gdb' to
	easily launch a native debugging session for your NDK-generated machine code.

	The script is located at the top-level directory of the NDK, and shall
	be invoked from the command-line when in your application project
	directory, or any of its sub-directories. For example:

	cd $PROJECT
	$NDK/ndk-gdb

	Where $NDK points to your NDK installation path. You can also create an
	alias or add $NDK to your PATH to avoid typing it every time.

	IMPORTANT: Native debugging can only work if all these conditions are met:

	1. Your application is built with the 'ndk-build' script:

	Building with the legacy "make APP=<name>" method is not
	supported by ndk-gdb.

	2. Your application is debuggable:

	In other words, your AndroidManifest.xml has an <application>
	element that sets the android:debuggable attribute to "true"

	3. You are running your application on Android 2.2 (or higher):

	ndk-gdb will not work if you try to run your application on
	previous versions of the system. That does not mean that your
	application should target the Android 2.2. API level, just
	that the debugging session should happen on a 2.2+ device or
	emulator system image.

	IMPORTANT IMPORTANT IMPORTANT !!

	If you are using the ADT Eclipse plug-in to build your
	application, make sure you're using version 0.9.7 or
	later.

	If you are using the 'ant' build tool, make sure that you
	have the latest revision of the SDK Platform components.
	The following minimal revisions are required:

	Android 1.5 r4
	Android 1.6 r3
	Android 2.1 r2
	Android 2.2 r1

	These should be available through the SDK updater.

	If these conditions are not met, the generated .apk will
	not contain required support files and native debugging
	will not be possible.

	'ndk-gdb' handles many error conditions and will dump an informative error
	message if it finds a problem. For example, it:

	- checks that adb is in your path.

	- checks that your application is declared debuggable in its manifest.

	- checks that, on the device, the installed application with the same
	package name is also debuggable.


	By default, ndk-gdb will search for an already-running application process,
	and will dump an error if it doesn't find one. You can however use the --start
	or --launch=<name> option to automatically start your activity before the
	debugging session.

	When it successfully attaches to your application process, ndk-gdb will give
	you a normal GDB prompt, after setting up the session to properly look for
	your source files and symbol/debug versions of your generated native
	libraries.

	You can set breakpoints with 'b <location>' and resume execution with 'c'
	(for 'continue'). See the GDB manual for a list of commands.

	IMPORTANT: When quitting the GDB prompt, your debugged application process
	will be stopped! This is a gdb limitation.

	IMPORTANT: The GDB prompt will be preceded by a long list of error messages,
	where gdb complains that it cannot find various system libraries
	(e.g. libc.so, libstdc++.so, liblog.so, libcutils.so, etc...)

	This is normal, because there are no symbol/debug versions of
	these libraries corresponding to your target device on your
	development machine. You can safely ignore these messages.

	II. Options:
	------------

	To see a list of options, type 'ndk-gdb --help'. Notable ones are:

	--verbose:
	Print verbose information about the native debugging session setup.
	Only needed to debug problems when you can't connect and that the
	error messages printed by ndk-gdb are not enough.

	--force:
	By default, ndk-gdb aborts if it finds that another native debugging
	session is running on the same device. Using --force will kill the
	session, and replace it with a new one. Note that the debugged program
	is not killed and will be stopped again.

	--start:
	By default, ndk-gdb will try to attach to an existing running instance
	of your application on the target device. You can use --start to
	explicitly launch your application before the debugging session.

	NOTE: This launches the first launchable activity listed from your
	application manifest. Use --launch=<name> to start another one.
	See --launch-list to dump the list of such activities.

	--launch=<name>:
	This is similar to --start, except that it allows you to start a specific
	activity from your application. This is only useful if your manifest
	defines several launchable activities.

	--launch-list:
	Convenience option that prints the list of all launchable activity names
	found in your application manifest. The first one will be used by --start

	--project=<path>:
	Specify application project directory. Useful if you want to launch
	the script without cd-ing to the directory before that.

	--port=<port>:
	By default, ndk-gdb will use local TCP port 5039 to communicate with
	the debugged application. By using a different port, it is possible
	to natively debug programs running on different devices/emulators
	connected to the same development machine.

	--adb=<file>:
	Specify the adb tool executable, in case it is not in your path.

	-d, -e, -s <serial>:
	These flags are similar to the ADB ones and allow you to handle the
	case where you have several devices/emulators connected to your
	development machine.

	-d: Connect to a single physical device
	-e: Connect to a single emulator device
	-s <serial>: Connect to a specific device or emulator
	where <serial> is the device's name as listed
	by the "adb devices" command.

	Alternatively, you can define the ADB_SERIAL environment variable
	to list a specific device, without the need for a specific option.

	--exec=<file>:
	-x <file>:
	After connecting to the debugged process, run the GDB initialization
	commands found in <file>. This is useful if you want to do something
	repeatedly, e.g. setting up a list of breakpoints then resuming
	execution automatically.


	III. Requirements:
	------------------

	At the moment 'ndk-gdb' requires a Unix shell to run. This means that
	Cygwin is required to run it on Windows. We hope to get rid of this
	limitation in a future NDK release.

	The other NDK requirements apply: e.g. GNU Make 3.81 or higher.


	IV. Thread Support:
	-------------------

	If your application runs on a platform older than Android 2.3, ndk-gdb will
	not be able to debug native threads properly. Instead, the debugger will only
	be able to put breakpoints on the main thread, completely ignoring the
	execution of other ones.

	The root of the problem is complex, but is essentially due to a very unfortunate
	bug in the platform, which was only discovered lately.

	The gdbserver binary that comes with this NDK has special code to detect this
	condition at runtime and adapt its behaviour automatically (in other words,
	you don't have anything special to do when building your code).

	What this means in practical terms are:

	- If you are on Android 2.3, or a prior platform release which has had the
	platform bug-fix back-ported to it, you will be able to debug native
	threads automatically.

	- If you are not, you will only be able to debug the main thread
	(as in previous NDK releases). You will also see the following message
	when launching ndk-gdb (just before the gdb prompt):

	Thread debugging is unsupported on this Android platform!

	If you place a breakpoint on a function executed on a non-main thread, the
	program will exit with the following message in GDB:

	Program terminated with signal SIGTRAP, Trace/breakpoint trap.
	The program no longer exists.

	</pre></body></html>